Method of forming a spacer-expander

ABSTRACT

A method of making a spacer-expander for a dual rail piston oil ring of the type disclosed in U.S. Pat. No. 3,477,732. The spacer-expander is formed by progressively blanking a strip of flat metal stock to repetitively form successive incremental sections containing two marginal bands, a transverse strut and two legs extending in oppositely offset relation parallel to said strut. The legs are bent to their final inclined relationship with the bands while the strip is still flat. Then the strip is progressively bent into a channel configuration by progressive zone bending of the struts. Further features are set forth in the annexed description.

United States Patent Inventor Frank G. Warrick 1 2,697,865 12 1954 Norton 29/l56.6 x MuskegomMich- 2,834,096 5/1958 Norton 29/l56.6 1 pp 39,264 2,837,385 6/1958 Mayfield 277 140 1 Filed i/ 1970 3,181,875 5/1965 Shepard 277/140 Patented 1 1972 3,477,732 11/1969 Warrick 267/1.5 X [73] Assignee Sealed Power Corporation Muskegon, Mich. Pru nary Examiner-John F. Campbell Assistant Exammer-V1ctor A. Di Palma Attorney-Barnes, Kisselle, Raisch & Choate [54] METHOD OF FORMING A SPACER-EXPANDER Drawing ABSTRACT: A method of making a spacer-expander for a [52] US. Cl 29/156.6 dual mi] piston oil ring f the type disclosed in s p N0 [51] Int.Cl 823p 15/06 3 477 731 The spacelexpander is f d b progressivdy [50] Field of Search 29/156.6, Manking a Strip f fl t meta] stock to repetitively f Succes. ;267/1- 13 5; sive incremental sections containing two marginal bands, a 72/33513389405 transverse strut and two legs extending in oppositely offset relation parallel to said strut. The legs are bent to their final [561 Referencescmd inclined relationship with the bands while the strip is still flat. UNITED STATES PATENTS Then the strip is progressively bent into a channel configura- 2,111,258 3/1938 Zahodiakin 267/1.5 tion by progressive zone bending of the struts. Further fea- 2,482,990 9/1949 Olson 29/156.6 X tures are set forth in the annexed description.

13 15 ,16 11 18 14 19 7 70 v 4'': Ar \i 5' C! D" 0 A E3: E0

n\ m i i i 7O 72 74' 1 7a 84 72 74 74' \i, \e 14 W mama) m1 1 1912 31633280 SHEEI 1 OF 4 INVENTOR. FRANK C7. WARRICK ATTORNEYS PATENTEDJRHI 1% 316331260 sum 3 OF 4 1 VENTOR. FRANK G. V ARmCK ATTORNEYS alsaalzso PATENTED JAN] 1 I972 SHEEI 4 [IF 4 INVENT OR. FRANK G. WARRmK BY M ATTORNEYS METHOD OF FORMING A SPACER-EXPANDIER This invention relates to piston rings and more particularly to an improved method of forming a spacer-expander adapted to be used with one, but preferably two, thin metallic rails of a piston oil ring assembly for an internal combustion engine.

An object of the present invention is to provide an improved method of forming a spacer-expander of the type disclosed in U.S. Pat. No. 3,477,732, issued Nov. 1 1, I969 in the name of Frank G. Warrick, inventor herein, and assigned to Sealed Power Corporation of Muskegon, Michigan, assignee of the present application.

More particularly, the present invention provides a method of forming the spacer-expander shown and described in connection with FIGS. 1-5 in the aforementioned patent in a manner which is economical, reliable, accurate, which lends itself to progressive die blanking and bending operations, which permits mass production of the spacer-expanders on a reliably repetitive basis with close tolerances in automatic machine setup, and in which the blank strip stock starting material is worked and stressed in blanking and bending it into the final product in a manner which cooperates with the various functions of the respective structural portions of the spacer-expander in its finished form.

Other objects as well as features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a plan view of an oil ring assembly incorporating one embodiment of a spacer-expander made by the method of the present invention and having portions broken away to illustrate details thereof.

FIG. 2 is an enlarged vertical sectional view taken on the line 2-2 of FIG. 1 with the oil ring assembly installed in the oil ring groove of a piston and compressed to operating diameter by the wall of the engine cylinder in which the piston is installed.

FIG. 3 is a fragmentary perspective view of the spacer-expander and associated rails of the oil ring assembly.

FIG. 4 is a fragmentary perspective view of a strip of the initial ribbon stock from which the spacer-expander is formed.

FIGS. 5, 6, 7, 8, 9, 10, 11 and 12 are fragmentary perspective views showing in sequence the progressive die blanking and bending steps of the method of the invention.

FIGS. 13 and 14 are sectional views taken respectively on the lines 13-13 and 14-14 of FIG. 12.

FIGS. l5, l6, l7, l8 and 19 are fragmentary vertical sectional views taken on the lines 15-15, 16-16, 17-17, 18- 18 and 19-19 of FIG. 12 illustrating in more detail the progressive strut bending steps and associated tooling for performing the steps to impart the progressive bending of the strip illustrated in FIG. 12.

FIGS. 20, 21 and 22 are enlarged fragmentary views of the left-hand bend portion of the strut and illustrating respectively the progressive zone working of the strut imparted in FIGS. 15-19 inclusive.

FIG. 23 is a fragmentary side elevational view of an induction heat treat step.

FIG. 24 is a fragmentary plan view of the progressive coiling step of the method.

FIG. 25 is a fragmentary plan view illustrating the strip cutoff step of the method.

FIG. 26 is a fragmentary plan view of a joint trim step of the method.

FIG. 27 is a fragmentary plan view of a joint bending step of the method.

Referring in more detail to the accompanying drawings, FIGS. 1, 2 and 3 illustrate a spacer-expander 58 used in connection with one or two rails 60 and 62 to form an oil ring assembly for use in the groove 54 of a piston 52 reciprocable in a cylinder 50, as set forth in more detail in the aforementioned U.S. Pat. No. 3,477,732, the disclosure of which is incorporated herein by reference. FIGS. 1, 2 and 3 correspond respectively to FIGS. 1, 5 and 3 of said patent except that the end joint structure consists of the T-shaped pad 275 disclosed in conjunction with FIGS. 12, I4 and 15 of said patent. Since the function and structure of spacer-expander 58 is fully set forth in the aforementioned patent, and the reference numerals used herein are the same as in FIGS. 1-5 of said patent, spacer-expander 58 will not be described in detail herein except as is incidental to the description of the method of forming the same pursuant to the present invention.

The first step of the method of the invention is the provision of a strip of thin flat ribbon metal stock (FIG. 4) which may be supplied from a suitable coil 102 of such stock for feeding in a generally straight horizontal path through a series of blanking and bending operations which preferably are continuously and automatically performed in a machine constructed pursuant to the disclosure of a copending U.S. Pat. application of Roy E. Overway and Frank G. Warrick, Ser. No. 39,499, filed on even date herewith, and entitled Machine for Forming Spacer-Expanders". However, it is to be understood that the method of the present invention may also be performed by hand or by other machines operable upon strip 100 wherein strip 100 is held stationarily and the punching and bending operations as described hereinafter are performed one at a time or in multiples in progressive punching and bending dies as will be better understood from the description which follows. Strip 100 preferably is made of stainless steel, and when being formed into spacer-expander 58 for use in a dual rail oil ring assembly 58-60-62 having a nominal operating diameter of 4 inches for use in a groove 54 having an axial width of 0.188 inch, strip 100 has, by way of example, a unit length of I 1.833 inches, a width of 0.434 inch and a thickness of 0.0 l 2 inch.

In accordance with one feature of the present method, strip 100 is oriented such that its upwardly facing side 104 remains so oriented throughout the steps of the method described in conjunction with FIGS. 4-22 inclusive, assuming that the blanking punches and bending dies are positioned above the strip and travel downwardly perpendicular to the plane of the strip on their working strokes. Also the upwardly facing surface 104 and strip 100 becomes the radially inner or interior surface of spacer-expander 58 in its final form. Thus in the die punching or blanking steps described subsequently herein with reference to FIGS. 5, 6, 7, 8 and 10, the punch on its working stroke will first strike surface 104 of strip 100 on a shearing stroke and will travel downwardly through the strip so that the burrs are formed on the underside of the strip, which later becomes the outer exterior surface of the spacerexpander 58. Hence such burrs will be stressed in compression when the spacer-expander is coiled to operating configuration in the step illustrated in FIG. 24. Also, the burrs will be exposed at the outer periphery of spacer-expander 58 where they may be readily removed by chemical and/or mechanical polishing equipment. With this orientation the scrap material removed from the strip falls by gravity and thus is easily collected in a suitable container. Also, the punching and bending of the strip from above simplifies the construction, mounting and support of the backup dies for these operations.

Another feature of the method is to feed strip 100 lengthwise simultaneously through a series of blanking and bending stations which perform blanking and bending operations on strip 100, the strip being intermittently advanced a distance equal to two sections or pitches, a pitch as used herein meaning an incremental distance lengthwise of the strip corresponding to the repeat of the pattern seen in blank 68 of FIG. 7 wherein the pitch length is labeled P" and represents the lengthwise or longitudinal distance from the center of one strut portion 74 to the center of the next adjacent strut portion 74. Hence as indicated in FIG. 8 one section is one pitch length long and contains one leg portion 76, one leg portion 78, and one strut portion 74. It also contains two parallel marginal bands 70 and 72 connected by strut 74 and running continuously along the margins of strip 100. The outer end of leg portion 76 is joined integrally to band 72 and the outer end of leg portion 78 is integrally joined to band 70. The free or inner ends of leg portions 76 and 78 terminate short of the opposite band. In a spacer-expander 58 constructed as shown in FIG. I having a total of 26 struts 74, the strip length per spacer-expander is made equal to 26 times P," plus two additional pitch lengths for a total of 28 P to provide material for the end joint tabs 275 mentioned previously.

Preferably, each blanking and bending operation is performed upon two adjacent pitches at a time, and strip 100 is fed lengthwise between each operation for a distance of two pitch lengths which may represent a distance of 0.600 inch. The strip is held stationary between each advance in accurately located position for registry with all of the punching and/or bending dies required to perform a different operation at each station corresponding to the separate figures shown in sequence herein in FIGS. 5, 6, 7, 8, 9, l and 11, and this same advance occurs in the operations of FIGS. 12-25 inclusive.

In the example given above, the first punching operation consists of simultaneously punching six parallel slots I06, 108, 110, 112, 114 and 116 which extend perpendicular to the length of strip 100 and are equally spaced lengthwise of the strip, the distance between the center of slot 106 and slot 112 being equal to the pitch length P. The material removed in this step consists of the six punchings 106-116 as shown in FIG. 5. Strip 100 is then indexed to advance it to the right as viewed in FIGS. 1-12 inclusive a distance of two pitch lengths. Then another six slots are punched in the strip. In the example given a total of 13 strikes of the six slot punches occur in sequence to form a total of 156 slots.

Then strip 100 is advanced another two pitch increment but the six slot punch step of FIG. 5 is skipped to thereby leave a blank end joint portion 118 (FIG. 6) in strip 100 from which two end tabs 275 are subsequently formed, one tab becoming the trailing end tab and the other the leading end tab of two adjacent spacer-expanders being sequentially formed from strip stock 102. However, in place of the slotting operation of FIG. 5 an interim operation is performed on the end joint portion 118 wherein, as shown in FIG. 6, a pair of short tandem slots 120 and 122 are punched in portion 118 in the space where slot 112 otherwise would have been punched. The punching of slots 120 and 122 produces the punchings 120' and 122 shown in FiG. 6. Slots 120 and 122 serve as locator slots in conjunction with a pawl stop mechanism (not shown) of a suitable strip-advancing mechanism utilizing the principle of strip overfeed and pull back to provide intermittent strip advance. One such mechanism is disclosed in U.S. Pat. No. 2,925,847, particularly in connection with FIGS. 4-9 thereof. When strip 100 is pulled back following a forward index the pawls engage slots 120 and 122 to thereby catch the strip and hold it in arcuately registered position for the simultaneous punching or forming operations of the method. The pawl stop mechanism is designed to catch the fourth slot 112 in each successive six-slot, two-section increment. Hence slots 120 and 122 in the end joint section 118 are likewise caught by the pawl stop when section 118 comes into registry with the stop mechanism.

Referring to FIG. 7, the next step in the method of the invention is to punch out a portion 76' of the strip located between slots 106 and 108, and a similar portion 78' located between slots 108 and 110. Preferably, a similar punching operation is performed simultaneously on the adjacent pitch between slots 112 and 114 and 116. This punching operation thus forms in each pitch a leg 76 between slots 106 and 108 and a leg 78 between slots 108 and 110. The material remaining between slots 110 and 112 and between slots 116 and 106 of the preceding six-slot series thus forms the two struts 74 in the two adjacent pitch lengths. This operation is repeated with each successive advance of strip 100 for a total of l3 strikes to produce, in the present example, 26 struts 74 and 26 each of associated leg portions 76 and 78. However, when skip portion 118 registers with the punch station for FIG. 7, preferably the operation of FIG. 7 is skipped and the punching operation of FIG 8 is performed.

In the step shown in FIG. 8, the first of two joint blanking operations is performed on skip portion 118 wherein six punches are employed to simultaneously blank out eight punchings 130, 132, 134, 136, 138, I40, 142 and 144. The portions of the strip 100 removed by this blanking operation leave intact the two marginal bands 70 and 72 as well as a center strip 146 running from the leading strut 74 of one spacer-expander blanking to the trailing strut 74 of the next preceding spacer-expander blanking. This blanking operation also leaves two cross strips 148 and 150 which are properly located to subsequently provide material for the cross bars 281 of the end tabs 275 as disclosed in the aforementioned U.S. Pat. No. 3,477,732 in conjunction with FIGS. l2, l4 and 15 thereof.

The first bending step of the method of the invention is illustrated in FIG. 9 wherein an upwardly inclined foot 82 is formed on the free end of each leg portion 76, and a similar upwardly inclined foot 84 is formed on the free end of each leg portion 78. Again, preferably the foot-bending operation of FIG. 9 is performed simultaneously on the four leg portions of two pitch lengths. This operation produces a bend line 82 between the foot 82 and the remaining portion of leg 76 which continues to lie in the plane of strip 100. A similar bend line is formed between foot 84 and leg portion 78. This operation is repeated for a total of 13 strikes in the example given above.

Referring to FIG. 10, a third punching or blanking operation is performed on skip portion 118 wherein punchings 70 and 72 are removed from the strip, leaving the center longitudinal strip 146 and the cross bars 281 of what will subsequently become the T-shaped pads 275. It is to be noted that be performing the main blanking operations on the skip portion 118 in two stages, first as shown in FIG. 8 and then in FIG. 10, the continuity of the marginal longitudinal bands 70 and 72 is retained in the continuous strip 100 through the several stations leading up to FIG. 10. This preserves the longitudinal strength of strip 100 as long as possible, the retention of the continuity of the side bands 70 and 72 thus reducing the tendency of the strip to buckle as it is pushed forward. Hence this is advantageous when strip 100 is advanced through the blanking and bending operations of the method by pushing the strip 100 in a strip feeding station located upstream of all the blanking and bending operations. Such a strip-feeding mechanism is disclosed in U.S. Pat. No. 2,925,847, which is also incorporated herein by reference for this aspect of its disclosure as well as for skip station punch and die structure.

Referring to FIG. 11, the next step is to bend the legs 76 and 78 in each section upwardly from the plane of strip 100 about a bend line located close to the inner edge of margins 70 and 72 to form the bends 88 and 90 in the legs 76 and 78 respectively. Preferably, this bending is performed in a single stage so that the final angle between legs 76, 78 and the plane of strip is the same as that between leg 76 and band 72 and leg 78 and band 70 as in the free-state condition of the spacerexpander 58 as shown in FIG. 4 of the aforementioned U.S. Pat. No. 3,477,732. In conformity with the aforementioned two pitch sequential advance of strip 100, the two legs 78 and two legs 76 of two adjacent pitches are bent simultaneously in the step of FIG. 11. Hence in the example given above a total of 13 sequential bending strikes are required to complete the formation of the legs 76 and 78 of each spacer-expander 58.

The next step in the method of the present invention comprises a sequence of strut-bending operations as shown in FIGS. 12-22 inclusive wherein the flat strip 100, with the legs 76 and 78 bent up from the plane of the strip per the operation of FIG. 11, is progressively curled to impart a generally U- shaped channel configuration to the strip, as best seen in FIG. 14. Preferably this is accomplished by progressively bending struts 74 in two bending zones equally spaced outwardly from the center of strut 74 as the strip is advanced through a progressive die-bending station equipped with a series of die punches and cooperating die shoes as well as a backup and stripper shoe as shown in FIGS. 15-22 inclusive. In the example under consideration wherein strip 100 is being advanced intermittently two pitch lengths at a time, these punches and dies may range in even number multiples from about 10 to about 20 punches. Assuming, for example. that these punches are numbered consecutively 1-10 inclusive in the direction of strip travel, the odd numbered punches operate on a leading strut 74 of one two-pitch length increment while the even numbered punches operate on a trailing strut 74 of this increment, all punches preferably operating simultaneously through one working cycle per each two-pitch index of the strip. 1

FIGS. 15-19 inclusive illustrate the progression of the first strut 74 of the two adjacent struts 74 and 74 of each two pitch increment through this progressive bending station. FIG. 20 illustrates the progressive bending of strut 74 imparted successively in the operations of FIGS. 15, 16 and 17 with respect to the left hand bending zone of the strut as viewed in FIGS. 15, 16 and 17. FIG. 21 illustrates the further bending progression imparted in the operation of FIG. 18, and FIG. 22 illustrates the still further bending progression imparted in the operation of FIG. 19.

Referring first to FIG. 15, the shape of the leading strut 74 is shown after it has been bent by being struck by the second punch 150 against its associated left and right die shoes 152 and 154 respectively and backup punch 156. Prior to being so struck this leading strut 74 is advanced while in its flat unbent condition (shown at the left hand end of strip 100 in FIG. 12) into registry with the flat flush horizontal surfaces 158 and 160 of shoes 152 and 154 respectively. During this strip advance punch 150 is raised clear of the strip and backup punch 156 is elevated so that its upper surface 162 is raised slightly above the plane of surfaces 158 and 160. Preferably, backup punch 156 extends continuously through all punch stations and is elevated to its raised position when the respective upper punches are raised to their uppermost position so that the central portions of struts '74 and 74 can slide along surface 162 during each increment of strip advance, the strip thereby being elevated clear of the forming shoes at each station.

Each of the two bends in loading strut 74 are formed at the same time in progressive working stages shown herein by way of example as five stages identified as A, B, C, D, and E cor responding to punch stations Nos. 2, 4, 6, 8 and 10. Accordingly, strut 74 is operated on at stations Nos. 2, 4, 6, 8 and 10 by the tooling shown in FIGS. 15, 16, 17, 18 and 19 respectively. In station No. 2, the horizontal separation between punches 152 and 154, the radius R and R (FIG. of shoes 152 and 154 and the width as well as radii at the lower corners of punch 150 are properly correlated to produce a first bending of strut 74, changing it from its flat shape to the configuration shown in FIG. 15. This first bend is completed when punch 150 is bottomed on its downward working stroke against the strip stock and bottomed backup punch 156, this being the position of the parts shown in FIG. 15. This change in configuration of strut 74 from its flat horizontal position to the first upwardly inclined position labeled A is shown in broken and solid lines respectively in FIG. 20, only the angular inclination of the left portion of strut 74 being shown in FIG. 20. The bending forces imparted by the tooling in station No. 2 are concentrated in a small segment of strut 74, labeled A in FIG. 20, causing segment A to be bent, thereby cold working and permanently deforming only this portion of the strut. This results from portion A of strip 74 being bent upwardly against the innermost angular increment 164 of thercorner radius of punch 150. The remaining portion of strip 74 outwardly of segment A extends tangentially from radius segment 164 up wardly and outwardly to its tangential contact with the radius R of shoe 152. A like segment zone working is imparted to the right-hand bend zone of strut 74 (not shown in FIG. 20) in station No. 2.

It is to be understood that while the tooling of FIG. 15 is imparting the first bend to strut 74, a similar punch bending operation is being performed on the companion trailing strut 74' in punch station No. 1. However the inclination imparted by the tooling of station No. 1 to the extremities of strut 74' elative to its central portion is less than that imparted in station No. 2 to strut 74. For example, FIG. 13 illustrates the amount of bending imparted in station 1, which may be on the order of 15 upwardly from horizontal, whereas the amount of bending imparted to the leading strut 74 in station 2 may be on the order of 30 upwardly from the horizontal as shown in FIG. 15. A similar difference exists between each of the successive even and odd numbered punch stations. Hence the transition in the strip lengthwise thereof is smooth and gradual as the strip is curled from its flat condition to the final channel shaped configuration wherein, as illustrated in FIG. 14, the extremities 96 and 98 of each strut 74 and 74 are inclined slightly toward one another by about 10 inwardly from the vertical, i.e.. at an angle of about relative to the central flat portion 86 of the strut.

In the second stage of the progressive bending operation of the present invention, strut 74 is bent in station No. 4 from its configuration A of FIG. 15 to a configuration B illustrated in FIG. 16 by a punch 166, associated die shoes 168 and 170 and backup punch 1172. Preferably the tooling employed in station No. 4 has the same shape and size as the tooling in station No. 2, the only difference being that punch 166 and backup punch 172 bottom farther downwardly below the horizontal plane of the upper surfaces 174 and 176 of shoes 168 and 170. Strut 74 is thus bent in a localized zone of working contiguous with and outwardly of segment A, causing permanent deformation of only segment B in this station as the strut is bent against the increment 178 of the corner radius of punch 166.

When the strip is indexed a third time, strut 74 moves into registry with the tooling at station 6 wherein it is operated upon by punch 180, associated shoes 182 and 184 and backup punch 186. Again this tooling is the same as that used in the previous bending stations but punch bottoms even further downwardly from the plane of the upper surfaces 188 and 190 of shoes 182 and 184, thereby bending strut 74 from its B (FIG. 16) to its C configuration (FIG. 17). In so bending, strut 74 is cold worked in still another localized zone of working contiguous with and outwardly of segment B, again causing permanent deformation of only segment C in this station as strut 74 is bent against the increment 192 of the corner radius of punch 181). This sequence of zone working is best indicated in the composite view of FIG. 20.

In the fourth bending operation, the progression of the working zones is reversed so that strut 74 is now worked in a localized zone of bending contiguous with the inner boundary of segment A and disposed inwardly thereof, as shown in FIG. 21. This is accomplished at station No. 8 (FIG. 18) by utilizing a punch 194 and backup punch 196, both of narrower width (the horizontal dimension in the plane of the drawing) than the previous uniform width punches 150, 166 and 180, and by bringing the associated die shoes I98 and 200 closer together. However, the penetration of punch I94 below the horizontal plane of the upper surfaces 202 and 204 of shoes 198 and 200 remains the same as that of the previous punch 180 in the sixth station. This imparts a further bending to strut 74 to change its configuration from the shape C to the shape D shown in broken and solid lines in FIG. 21. This narrowing of punches 194 and 196 causes strut 74 to permanently deform by bending about the innermost increment 206 of the comer radius of punch 194, thereby forming segment D while bringing the previously bent segments. A, B and C against the mating sur' face of the comer of punch 194.

In the last station No. 10 (FIG. 19) the horizontal distance between the forming shoes 208 and 210 of this station is again narrowed, as in the corresponding dimension of the punch 212 and associated backup punch 214. However, the vertical penetration of punch 212 relative to the upper surfaces of shoes 208 and 210 remains the same as in the previous stations 8 and 6.

The progressive narrowing of the punches and the smaller spacing between the associated die shoes which occurs in stations 8 and 10 relative to station 6 is illustrated schematically in the vertically aligned views of FIGS. 20, 21 and 22 wherein the vertical phantom lines 186, 196 and 214' represent extensions of the left edge of the backup punches 186, 196 and 214 in stations 6, 8 and 10 respectively.

The side surfaces 216 and 218 of punch 212 are formed to the final angle to which the strut 74 is shaped as shown in FIG. 19. The further narrowing of the punch in station No. 10 causes the next localized zone of working to occur contiguous with segment D and inwardly thereof as shown in FIG. 22 wherein strut 74 is bent from the shape D (broken lines) to the shape E (solid lines). This bending occurs against the innermost increment 220 of the corner of punch 212, causing pennanent deformation of segment E while bringing segments D, A, B, and C against the comer of punch 212.

Due to the fact that the previously worked zones A, B, C and D have produced a total bend in the strut of about 80 relative to the flat central portion of the strut, the final additional bend produced in segment E provides a total bend of 100 thereby bringing the portion 96 of strut 74 against the inwardly inclined side surface 218 of punch 212. Thus, portions 96 and 98 (FIG. 14) are brought to their final shape E wherein they are inclined towards one another even through the working strokes of the punches all occur in a vertical direction and there is no horizontal movement of the associated shoes 208 and 210. In addition, the 100 zone of working in the two bending zones of strut 74 is accomplished in approximately equal increments, preferably in five stages. Hence the strut is stressed through successive increments to produce a relatively large zone of cold working and permanent deformation without being overstressed, i.e., without causing cracking or breakage, even though it has been bent about a relatively small radius through more than a right angle.

It is to be understood that the progression of strut 74 through stations 1, 3, 5, 7 and 9 follows a similar sequence but at intermediate bending angles to produce in sequence intermediate shapes A", B", C, D" and E" (FIG. 12) respectively in order to impart the aforementioned smooth transition to strip 100 as it is curled to the final U-shaped configuration while being advanced in the direction of the arrow in FIG. 12. This difference between the even and odd numbered diebending stations thus insures that no ripple occurs in the two continuous marginal bands 70 and 72 as a result of the bending stresses imparted in progressing from one strut 74 to the next strut 74 during the progressive bending stages.

It also is to be understood that when the strip is advanced to move strut 74 from the station 8 to station 10, strut 74 will have the shape D as it is brought into registry with shoes 208 and 210 and is aligned vertically beneath the raised punch 212. Hence when punch 212 is brought down on its downward working stroke, it will clear the margins 70 and 72. The same condition obtains at station No. 9 with respect to its corresponding punch (not shown). However, once punch 212 (and likewise the upper punch of station No. 9) has bottomed in its downward forming stroke, the marginal bands 70 and 72 will now lie inwardly of the lateral extremities at the lower corners of punch 212. Hence the strip will now cling to punch 212 and hence will be lifted when the punch is retracted vertically upwardly from the position shown in FIG. 19.

Accordingly, a stripper plate 222 is provided as shown in broken lines in FIG. 19 which extends horizontally between the punches of stations Nos. 9 and 10 and preferably also of stations Nos. 7 and 8. Plate 222 is maintained stationary at a given elevation just above raised level of the strip during strip advance. Thus when punch 212 is lifted, margins 70 and 72 will strike plate 222 to stop further upward movement of the strip while punch 212 is lifted further until the nose of the punch has been cleared from between bands 70 and 72. As the punch is being withdrawn from the strip, the 10 inclination of its side surfaces 216 and 218 serves to cam apart the portions 96 and 98 of the strut so that the punch nose can clear the strip, the spring material of the strip allowing it to yieldably flex apart and causing it to spring back to the final configuration once the punch has cleared the same.

It also will be understood that the end joint zone 118 of strip 100 produced in the operations shown in FIGS. 8 and 10 will not be bent as it travels through the progressive zone working bending operation of stations l-10 inclusive because the portions 281 terminate laterally inwardly of the innermost bending zone E. Hence portions 281 are always in registry with the horizontal flat surface of the upper and lower punches throughout this operation.

Due to the progressive curling ofstrip from the flat condition of FIG. 11 to the final channel or U-shaped configuration illustrated in FIGS. 2 and 14, the previously bent legs 76 and 78 will move from their upright position to a mutually crossed position wherein their respective feet 82 and 84 project beyond the opposite marginal band and through the space available between the adjacent strut and companion leg, as best seen in FIGS. 3 and 12.

The next step in the method of the invention is illustrated in FIG. 23 wherein the now U-shaped strip 100 is advanced lengthwise through a suitable induction heating coil 224 to provide a stress relieving heat treatment in a conventional manner.

The next step of the method is the coiling of the channel shaped strip into the circular configuration of the spacer-expander 58 shown in FIG. 1, this coiling operation being partially illustrated in FIG. 24. In this station the strip still is being intermittently advanced two pitch lengths at a time in the direction of the arrow in FIG. 24. The strip is brought between suitable bending dies which operate on a portion 230 of the strip to impart the proper radius to this portion of the strip in a single stroke operation which is repeated on successive increments 230. Hence by the time the leading joint portion 232 of one spacer-expander length has traveled through almost a full circle the trailing joint portion 234 comes into registry with a joint cutoff station located just upstream from the strip coiling dies. Preferably, the strip is guided as it is fed out of the coiling station so that the leading joint portion 232 is offset to one side of the strip being fed into the coiling station. Although this imparts a slight spiral shape to the strip as it is being coiled into a circular configuration, the lead signal of the spiral is so small that this does not permanently deform the strip out of a plane perpendicular to the axis of the coiled spacer-expander.

Then, in the next step of the method, the joint zone 118 of the strip is subjected to a joint cutoff operation as illustrated in FIG. 25. A suitable shearing die set severs the strip by cutting portion 146 midway between portions 281 along a cut line indicated by the arrow in FIG. 25. This operation is performed after the last portion of the strip adjacent the trailing end 234 has been coiled in zone 230 to the radius of the coiling die set. Thus control of the strip is maintained and it is advanced from coil 102 (FIG. 4) through all of the blanking and bending operations of FIGS. 524 as a continuous length of material, the individual spacer-expanders finally being severed from the strip at the cutoff station of FIG. 25.

To complete the forming of each spacer-expander 58, a final trimming and bending operation is performed on the end joints of the spacer-expander after severance of the continuous strip 100. Referring to FIG. 26, the coiled spacer-expander is suitably fixtured and the portion of strip 146 extending from the cross tab 281 to the free end of strip 146 is removed by a suitable blanking operation to thereby impart the T-shaped configuration of pad 275 as shown in FIG. 12 of the aforementioned Warrick U.S. Pat. No. 3,477,732. Finally, strip 146 is bent as shown in FIG. 27 at a point near the end strut 74 to thereby position the crossbar 281 of the end pad 275 in a plane perpendicular to the bands 70 and 72 of the spacer-expander as shown in solid lines in FIG. 27 and as shown in FIGS. 14, 15 and 16 of the aforementioned US. Pat. No. 3,477,732.

The spacer-expander 58 thus formed by the abovedescribed method may be subjected to further electrical or chemical polishing operations to deburr and finish the same, and also may be plated or given other conventional surface treatments as desired.

From the foregoing description, it now will be apparent that the method of the present invention provides an efficient progression of working steps well adapted for automated blanking and bending equipment to enable accurate, closetolerance yet high-speed mass production of the spacer-expander 58 disclosed in the aforementioned US. Pat. No.

3,477,732. The performance of the blanking steps in the successive stages described previously reduces the amount of material removed at each station and preserves the longitudinal compressive strength of the strip so that it can be advanced by one feeding mechanism located upstream of the ini tial blanking operation of FIG. 5. The bending of the legs 76 and 78 upwardly from the flat strip prior to the bending of the struts 74 simplifies bending of the strip to its final channel configuration. It also permits all bending operations as well as blanking operations to be perfonned from above so that all punches travel on vertical strokes and can travel simultaneously. As indicated previously, punching from above places the burrs on the outer periphery of struts 74 where they are stressed in compression when the spacer-expander is opened to operating diameter, and this also greatly facilitates removing the burrs in a deburring operation. Also, orienting the strip stock 1100 so that the inner periphery of the finished spacer-expander 58 is facing upwardly toward the vertically reciprocating blanking and bending punches simplifies the structure and mechanism required to back up the strip during these operations. The progressive zone bending of the struts 74 and 74 prevents overstressing of the same and makes it possible to impart the inclination of the bands 70 and 72 toward one another in a vertical stroke operation without requiring horizontally moving dies.

Iclaim:

1. A method of making a spacer-expander comprising the steps of:

1. providing a strip of the flat ribbon metal stock;

2. blanking said strip to repetitively form successive incremental sections wherein each section comprises two parallel bands extending lengthwise of the strip and defining the side margins thereof, a transverse strut spaced lengthwise of the strip equidistant from the struts of adjacent sections and at least one leg with said leg extending parallel to said strut and offset lengthwise of the strip from said strut, one end of said leg being connected to one of said first and second bands and the free end of the leg terminating short of the opposite one of said first and second bands;

. bending said leg at an angle corresponding to the final free-state inclination of the leg in said spacer-expander relative to its contiguous band; and,

. bending said struts in a progressive bending operation to impart a channel-shaped configuration to said strip when viewed in a radial cross section of the finished spacer-expander, whereby two bends are formed in each strut at the ends of what is to become an intermediate axially extending portion of each strut, said strut bending being performed in stages whereby a separate segmental increment of each of said bends of said strut is worked in each stage, said increments in each of said bends being contiguous to define the total curvature of the associated bend.

2. The method as set forth in claim 1 wherein said progressive bending of each of said bends in each strut is performed in a first stage on an intermediate one of said segments and then in another successive stage on a segment disposed outwardly from said first segment and then in a still further successive stage on a segment located inwardly of said intermediate segment.

3. The method as set forth in claim 1 wherein said step (3) is performed in advance of said step (4) such that said legs of each section assume their final position in said spacer-expander as said strip is curled to said channel-shaped configuration by said bending of said struts in said step 4).

4. The method as set forth in claim 1 wherein said strip is intermittently advanced two sections at a time and then held stationarily while all of said operations are simultaneously performed on successive sections.

5. The method as set forth in claim 4 wherein said progressive bending of said struts is performed in an even number multiplicity of bending punch and die stations wherein punch and die means of even numbered stations operate on one strut and the punch and die means of odd numbered stations operate on the next successive strut and wherein a further bending angle is imparted in each successive station of said multiplicity of stations.

6. The method as set forth in claim 5 wherein said stations are at least approximately 10 in number and the first six stations have identical forming punches and bending shoes, and the first portion of the progression in bending is obtained by progressively deeper penetration of the forming punches between their individually associated pair of laterally spaced forming die shoes in the first six stations, and wherein the last four stations further bending is imparted by confining said strut between progressively more narrowly spaced forming die shoes and the associated strut is struck with progressively narrower punches.

7. The method as set forth in claim 4 wherein said blanking step (2) comprises,

a. blanking six narrow transversely extending slots in each two adjacent sections of the flat strip whereby, considering the slots as being consecutively numbered one through six in the direction of strip travel, said first slot defines the leading edge of one strut next following said two sections, said third and fourth slots define the trailing and leading edges respectively of the trailing strut of said two sections and said sixth slot defines the trailing edge of the leading strut,

b. skipping said slot blanking operating in an end joint zone having a length equal to two sections,

c. forming a strip advance slot means in said end joint zone in a portion thereof which is to be subsequently removed,

d. removing by blanking two diagonally related portions of said strip between said first and second slots and said second and third slots and likewise removing by blanking two diagonally related portions of said strip between said fourth and fifth slots and said fifth and sixth slots,

e. bending the free ends of the diagonally related portions remaining after said step (d) to thereby form the free ends of four legs at an angle inclined upwardly from the plane of said strip, and

. then performing said bending operation of step (3) by bending said legs up from the plane of said strip about a bend line adjacent the associated marginal band.

8. The method as set forth in claim 7 wherein said end joint zone is fon'ned in two blanking stages, the first of said two stages leaving said bands at the margin of said strip uninterrupted and leaving a central longitudinally extending strip connecting the leading and trailing struts bounding said end joint zone, the second of said two stages comprising removing by blanking said bands and leaving said central strip intact.

9. The method as set forth in claim 1 wherein said strip stock is oriented with the surface thereof which faces the interior of said spacer-expander in its finished fonn facing upwardly and said blanking and bending steps are performed by punch means and die means movable vertically relative to one another perpendicular to the plane of said strip.

10. The method as set forth in claim 9 wherein said legs are formed by being bent upwardly from the plane of said strip and said struts are bent by punching downwardly a central portion of each strut and by bending upwardly the portions of each strut between said central portion and said marginal bands.

Ill. The method as set forth in claim 9 wherein said strip is coiled into a circle by bending successive increments of said strip after performing the steps recited in claims 1 and 7.

12. A method making a spacer-expander comprising the steps of:

1. providing a strip of the flat ribbon metal stock;

2. blanking said strip to repetitively form successive incremental sections wherein each section comprises two parallel bands extending lengthwise of the strip and defining the side margins thereof, a transverse strut spaced lengthwise of the strip equidistant from the struts of adjacent sections and first and second legs with the legs extending parallel to said strut and offset lengthwise of the strip, one end of said first leg being connected to said first band and one end of said second leg being connected to said second band and the free ends of the legs terminating short of the opposite band;

. bending said legs at least partially toward the final inclination of the leg relative to its contiguous band in said spacer-expander;

4. bending said struts at spaced zones to impart a channelshaped configuration to said strip when viewed in a radial cross section of the finished spacer-expander; and

. intermittently advancing said strip two sections at a time and then holding it stationarily while all of said operations of steps (2), (3), and (4) are simultaneously performed on successive sections.

13. The method as set forth in claim 12 wherein said blanking step (2) comprises,

a. blanking six narrow transversely extending slots in each two adjacent sections of the flat strip whereby, considering the slot as being consecutively numbered one through six in the direction of strip travel, said first slot defines the leading edge of one strut next following said two sections, said third and fourth slots define the trailing and leading edges respectively of the trailing strut of said two sections and said sixth slot defines the trailing edge of the leading strut, skipping said slot blanking operation in an end joint zone having a length equal to two sections,

c, forming a strip advance slot means in said end joint zone LII in a portion thereofwhich is to be subsequently removed,

d. removing by blanking two diagonally related portions of said strip between said first and second slots and said second and third slots and likewise removing by blanking two diagonally related portions of said strip between said fourth and fifth slots and said fifth and sixth slots,

. bending the free ends of the diagonally related portions remaining after said step (d) to thereby form the free ends of four legs at an angle inclined upwardly from the plane of said strip, and

f. then performing said bending operation of step (3) by bending said legs up from the plane of said strip about a bend line adjacent the associated marginal band.

14. The method as set forth in claim 13 wherein said end joint zone is formed in two blanking stages, the first of said two stages leaving said bands at the margin of said strip uninterrupted and leaving a central longitudinally extending strip connecting the leading and trailing struts bounding said end zone, the second of said two stages comprising removing by blanking said bands and leaving said central strip intact.

15. The method as set forth in claim 14 wherein said strip stock is oriented horizontally with the surface thereof which faces the interior of said spacer-expander in its finished form facing upwardly and said blanking and bending operations are performed by punch means operating in vertical strokes in cooperation with associated die means.

16. The method as set forth in claim 15 wherein said legs are formed by being bent upwardly from the plane of said strip and said struts are bent by punching down a central portion of each strut and bending up the portions of the strut between said central portion and said marginal bands.

mg 4 UNITED STATES PATENT ()FMC CERTH ECATE 0F CORRECTIQN Patent 3,633,260 Dated January ll, 1972 Inventor(s) Frank W rick It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1 line 68, cancel "connection" and insert ---con'junction.

Column 4 line 30, cancel "be" and insert -by--..

Column 5 Line 37, cancel "loading" and insert leading-; line 74, cancel "elative" and insert rela-. tive----.

Column 6 Line 64, cancel "in" and insert -is--.

Column 7 line 18, cancel "through" and insert -though--.

Column'8 line 36, cancel "signal" and insert --angle;--.

Column 10 line 15, after "wherein" insert in--; line 32,, cancel "operating" and insert -l-operation-;

line 71, after "method" insert -of--.

Column 11, line 24, cancel ''slot" and insert --slots..

Signed and sealed this 22nd day of August 1972.

h 1 I EAL) Attest:

L EDwARD M.FLETcH-E '{JR. ROBERT GOTTSCHALK J Attesting Officer Commissioner of Patents 

1. A method of making a spacer-expander comprising the steps of:
 1. providing a strip of the flat ribbon metal stock;
 2. blanking said strip to repetitively form successive incremental sections wherein each section comprises two parallel bands extending lengthwise of the strip and defining the side margins thereof, a transverse strut spaced lengthwise of the strip equidistant from the struts of adjacent sections and at least one leg with said leg extending parallel to said strut and offset lengthwise of the strip from said strut, one end of said leg being connected to one of said first and second bands and the free end of the leg terminating short of the opposite one of said first and second bands;
 3. bending said leg at an angle corresponding to the final freestate inclination of the leg in said spacer-expander relative to its contiguous band; and,
 4. bending said struts in a progressive bending operation to impart a channel-shaped configuration to said strip when viewed in a radial cross section of the finished spacer-expander, whereby two bends are formed in each strut at the ends of what is to become an intermediate axially extending portion of each strut, said strut bending being performed in stages whereby a separate segmental increment of each of said bends of said strut is worked in each stage, said increments in each of said bends being contiguous to define the total curvature of the associated bend.
 2. blanking said strip to repetitively form successive incremental sections wherein each section comprises two parallel bands extending lengthwise of the strip and defining the side margins thereof, a transverse strut spaced lengthwise of the strip equidistant from the struts of adjacent sections and at least one leg with said leg extending parallel to said strut and offset lengthwise of the strip from said strut, one end of said leg being connected to one of said first and second bands and the free end of the leg terminating short of the opposite one of said first and second bands;
 2. The method as set forth in claim 1 wherein said progressive bending of each of said bends in each strut is performed in a first stage on an intermediate one of said segments and then in another successive stage on a segment disposed outwardly from said first segment and then in a still further successive stage on a sEgment located inwardly of said intermediate segment.
 2. blanking said strip to repetitively form successive incremental sections wherein each section comprises two parallel bands extending lengthwise of the strip and defining the side margins thereof, a transverse strut spaced lengthwise of the strip equidistant from the struts of adjacent sections and first and second legs with the legs extending parallel to said strut and offset lengthwise of the strip, one end of said first leg being connected to said first band and one end of said second leg being connected to said second band and the free ends of the legs terminating short of the opposite band;
 3. bending said legs at least partially toward the final inclination of the leg relative to its contiguous band in said spacer-expander;
 3. The method as set forth in claim 1 wherein said step (3) is performed in advance of said step (4) such that said legs of each section assume their final position in said spacer-expander as said strip is curled to said channel-shaped configuration by said bending of said struts in said step (4).
 3. bending said leg at an angle corresponding to the final free-state inclination of the leg in said spacer-expander relative to its contiguous band; and,
 4. bending said struts in a progressive bending operation to impart a channel-shaped configuration to said strip when viewed in a radial cross section of the finished spacer-expander, whereby two bends are formed in each strut at the ends of what is to become an intermediate axially extending portion of each strut, said strut bending being performed in stages whereby a separate segmental increment of each of said bends of said strut is worked in each stage, said increments in each of said bends being contiguous to define the total curvature of the associated bend.
 4. The method as set forth in claim 1 wherein said strip is intermittently advanced two sections at a time and then held stationarily while all of said operations are simultaneously performed on successive sections.
 4. bending said struts at spaced zones to impart a channel-shaped configuration to said strip when viewed in a radial cross section of the finished spacer-expander; and
 5. intermittently advancing said strip two sections at a time and then holding it stationarily while all of said operations of steps (2), (3), and (4) are simultaneously performed on successive sections.
 5. The method as set forth in claim 4 wherein said progressive bending of said struts is performed in an even number multiplicity of bending punch and die stations wherein punch and die means of even numbered stations operate on one strut and the punch and die means of odd numbered stations operate on the next successive strut and wherein a further bending angle is imparted in each successive station of said multiplicity of stations.
 6. The method as set forth in claim 5 wherein said stations are at least approximately 10 in number and the first six stations have identical forming punches and bending shoes, and the first portion of the progression in bending is obtained by progressively deeper penetration of the forming punches between their individually associated pair of laterally spaced forming die shoes in the first six stations, and wherein the last four stations further bending is imparted by confining said strut between progressively more narrowly spaced forming die shoes and the associated strut is struck with progressively narrower punches.
 7. The method as set forth in claim 4 wherein said blanking step (2) comprises, a. blanking six narrow transversely extending slots in each two adjacent sections of the flat strip whereby, considering the slots as being consecutively numbered one through six in the direction of strip travel, said first slot defines the leading edge of one strut next following said two sections, said third and fourth slots define the trailing and leading edges respectively of the trailing strut of said two sections and said sixth slot defines the trailing edge of the leading strut, b. skipping said slot blanking operating in an end joint zone having a length equal to two sections, c. forming a strip advance slot means in said end joint zone in a portion thereof which is to be subsequently removed, d. removing by blanking two diagonally related portions of said strip between said first and second slots and said second and third slots and likewise removing by blanking two diagonally related portions of said strip between said fourth and fifth slots and said fifth and sixth slots, e. bending the free ends of the diagonally related portions remaining after said step (d) to thereby form the free ends of four legs at an angle inclined upwardly from the plane of said strip, and f. then performing said bending operation of step (3) by bending said legs up from the plane of said strip about a bend line adjacent the associated marginal band.
 8. The method as set forth in claim 7 wherein said end joint zone is formed in two blanking stages, the first of said two stages leaving said bands at the margin of said strip uninterrupted and leaving a central longitudinally extending strip connecting the leading and trailing struts bounding said end joint zone, the second of said two stages comprising removing by blanking said bands and leaving said central strip intact.
 9. The method as set forth in claim 1 wherein said strip stock is oriented with the surface thereof which faces the interior of said spacer-expander in its finished form facing upwardly and said blanking and bending steps are performed by punch means and die means movable vertically relative to one another perpendicular to the plane of said strip.
 10. The method as set forth in claim 9 wherein said legs are formed by being bent upwardly from the pLane of said strip and said struts are bent by punching downwardly a central portion of each strut and by bending upwardly the portions of each strut between said central portion and said marginal bands.
 11. The method as set forth in claim 9 wherein said strip is coiled into a circle by bending successive increments of said strip after performing the steps recited in claims 1 and
 7. 12. A method making a spacer-expander comprising the steps of:
 13. The method as set forth in claim 12 wherein said blanking step (2) comprises, a. blanking six narrow transversely extending slots in each two adjacent sections of the flat strip whereby, considering the slot as being consecutively numbered one through six in the direction of strip travel, said first slot defines the leading edge of one strut next following said two sections, said third and fourth slots define the trailing and leading edges respectively of the trailing strut of said two sections and said sixth slot defines the trailing edge of the leading strut, b. skipping said slot blanking operation in an end joint zone having a length equal to two sections, c. forming a strip advance slot means in said end joint zone in a portion thereof which is to be subsequently removed, d. removing by blanking two diagonally related portions of said strip between said first and second slots and said second and third slots and likewise removing by blanking two diagonally related portions of said strip between said fourth and fifth slots and said fifth and sixth slots, e. bending the free ends of the diagonally related portions remaining after said step (d) to thereby form the free ends of four legs at an angle inclined upwardly from the plane of said strip, and f. then performing said bending operation of step (3) by bending said legs up from the plane of said strip about a bend line adjacent the associated marginal band.
 14. The method as set forth in claim 13 wherein said end joint zone is formed in two blanking stages, the first of said two stages leaving said bands at the margin of said strip uninterrupted and leaving a central longitudinally extending strip connecting the leading and trailing struts bounding said end zone, the second of said two stages comprising removing by blanking said bands and leaving said central strip intact.
 15. The method as set forth in claim 14 wherein said strip stock is oriented horizontally with the surface thereof which faces the interior of said spacer-expander in its finished form facing upwardly and said blanking and bending operations are performed by punch means operating in vertical strokes in cooperation with associated die means.
 16. The method as set forth in claim 15 wherein said legs are formed by being bent upwardly from the plane of said strip and said struts are bent by punching down a central portion of each strut and bending up the portions of the strut between said central portion and said marginal bands. 